Anti-spin/anti-drift worm gear brake with bevel gear speed-up

ABSTRACT

An anti-spin, anti-drift assembly for installation on a railroad car plug-type door locking mechanism of the type having a gear segment rotatably mounted on the door, rotatable pipes mounted on the plug-type door, rods pivotally connected to the gear segment and to the rotatable pipes so that rotation of the gear segment brings about rotation of the pipes and opening and closing of the plug-type door. The anti-spin, anti-drift assembly includes a worm gear meshing with the gear segment. A speed up gear is located at one end of the worm gear. A drive gear meshes with the speed up gear and an operating wheel rotates the drive gear.

BACKGROUND OF THE INVENTION

Compression-sealing “plug-type” doors are provided for railway freight cars of the type in which ambient sealing of the interior is required. The closing and locking mechanisms for these type of doors have consisted of cranks depending from pairs of pipes rotationally secured to the doors and hand operated gear mechanisms to rotate the pipes and cranks between open and closed positions. Upon rotation of the pipes in a direction to apply a closing force to the plug-type door, a gasket in the door frame is usually compressed to seal the door. When the door is released, the cranks rotate in a direction which moves the door laterally outwardly so that it will clear the door frame for longitudinal movement along tracks or rails attached to the car above and below the door. Operating mechanisms of this type are powerful and when the door is compressedly sealed, a reverse torque is imparted to the operating handle or wheel as a result of the compression forces. A reverse torque can also arise from other factors such as load shifting inside the car which leans against the door or the force of the door's own weight when the car is tilted to lean outwardly. Operating mechanisms such as handles and wheels are routinely secured against counter-rotation in the door-opening direction by locking mechanisms of various types. However, to open a door, the handle or wheel lock must be released. If during rotation of the handle or wheel in the door-opening direction, the operator loses control of the handle or wheel, the handle or wheel will frequently spin, resulting in a highly dangerous condition to the operator and anyone else nearby. The drive mechanisms for the plug-type door opening and closing mechanisms include a gear segment mounted on a bearing plate attached to the plug-type door. Link rods connect the gear segment to the previously mentioned rotatable pipes. The gear segment is rotated by a gear or gears connected to the operating handle or wheel.

SUMMARY OF THE INVENTION

An anti-spin/anti-drift drive mechanism is provided which can be installed in a conventional opening and closing mechanism of a plug-type door to utilize the convention gear segment of this mechanism.

An object of this invention is a anti-spin/anti-drift drive mechanism which utilizes the self locking characteristics of a properly designed worm gear to prevent spinning and drifting of a plug-type door.

Another object of this invention is a drive mechanism using a worm gear with a speed up to overcome the large speed reduction of the worm gear so that a plug-type door can be opened with the same number of rotations of the operating handle or wheel that the current spur gear designs provide.

Other objects will be found in the following specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated more or less diagrammatically in the following drawings wherein;

FIG. 1 is a partial front elevational view of the mechanism of this invention with some parts omitted and other broken away for clarity of illustration and showing the mechanism in a door closed position;

FIG. 2 is a view similar to that of FIG. 1 but showing the mechanism in its door opened position;

FIG. 3 is an exploded view of the mechanism of FIGS. 1 and 2 with parts omitted for clarity of illustration, and;

FIG. 4 is a partial enlarged view of the meshing of the gears of the bevel gear set.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention is concerned with an anti-spin/anti-drift drive for the operating mechanism of a door of a railroad car, particularly a plug-type door. Both anti-spin/anti-drift drives and operating mechanisms for plug-type doors are well known in the railroad industry and examples of both are shown in U.S. Pat. No. 3,555,731 (Ross, Jr.) and U.S. Pat. No. 4,920,894 (Thoman), both of which patents are incorporated herein by reference for all purposes.

Referring now to the figures of the drawings, an outline of a plug-type door 11 (FIG. 3) is shown with a bearing plate 13 attached thereto in a conventional manner. A conventional door opening and closing mechanism 15 includes a gear segment 17 which is pivotally mounted on the bearing plate 13 by a shaft 19 (FIG. 3). Link rods 21 are pivotally connected to the gear segment 17 and are connected to rotatable pipes 23, only one of which is shown in FIGS. 1 and 2 of the drawings, which open and close the plug-type door 11 as described in U.S. Pat. No. 3,555,731 and U.S. Pat. No. 4,920,894. In the preferred form of the invention, the worm gear 25, its shaft 31 and the bevel gear 45 are integrally cast of ductile iron.

In this invention, the anti-spin/anti-drift mechanism includes a worm gear 25 having a single lead thread 27 which meshes with the teeth 29 of the gear segment 17. The worm gear includes a shaft 31 having sleeve bearings 33 and 35 which are journalled in mounting pillow blocks 37 and 39 fastened to the bearing plate 13. In this embodiment of the invention, the mounting pillow block 37 is permanently attached to the bearing plate 13 such as by welding. The mounting pillow block 39 is removably fastened to a base block 41 by removable threaded fasteners 43 with the base block permanently fastened to the bearing plate 13 as by welding. The provision of the removable mounting pillow block 39 permits the installation of the worm gear 25 in a conventional existing door opening and closing mechanism without a complete disassembly thereof. A bevel gear 45 is formed at one end of the worm gear 31. The bevel gear may be cast as an integral part of the worm gear and functions as a speed up gear to overcome the large speed reduction of the worm gear. In the preferred form of the invention, the worm gear 25, its shaft 31 and the bevel gear 45 are integrally cast of ductile iron.

The bevel gear 45 is part of a bevel gear set which includes a face gear 47 having axially extending teeth 49 that mesh with the teeth 51 of the bevel gear 45. The face gear 47 is mounted on a shaft 53 which is journalled in the bearing plate 13 at one end and is fastened at the opposite end of the shaft 53 to an operating member such as a wheel 55, although a conventional handle may also be used. A cover plate is located between the face gear 47 and the wheel 55, but has been omitted from the drawings for clarity of illustration. The wheel 55 is formed with a raised hex head hub 57 to permit the use of a power driven wrench to operate the wheel.

The provision of a worm gear 25 meshing with the teeth 29 of the gear segment 17 provides the locking friction to prevent unintended rotation of the operating wheel 55 whether the plug-type door is in its closed position or in being moving along the side of a railroad car in its open position. The self locking result is obtained when the worm thread is formed so that the tangent of the lead angle of the worm thread is greater than the coefficient of friction of the engaging surfaces of the gear segment 17 and the worm gear 25. For example, if the gear segment 17 and the worm gear 25 are cast of ductile iron, the lead angle of the worm thread is formed as 3.5 degrees. The tangent of the lead angle is 0.62. The coefficient of friction of the engaging surfaces of cast iron gear segment 17 and the worm gear 25 is 0.12. In accordance with the aforementioned formula, self-locking of the worm gear is achieved. For other materials having different coefficients of friction, the lead angle of the worm gear must be varied in accordance with the aforementioned formula to achieve self-locking. 

1. An anti-spin, anti-drift assembly for installation on a railroad car plug-type door locking mechanism of the type having a gear segment rotatably mounted on said plug-type door, rotatable pipes mounted on said plug-type door, rods pivotally connected to said gear segment and said rotatable pipes so that rotation of said gear segment brings about rotation of said pipes and opening and closing of said plug-type door, the improvement comprising: a worm gear meshing with said gear segment, a speed up gear at one end of said worm gear, a drive gear meshing with said speed up gear, and an operating member to rotate said drive gear.
 2. The anti-spin, anti-drift assembly of claim 1 in which said drive gear and said speed up gear form a bevel gear set.
 3. The anti-spin, anti-drift assembly of claim 1 in which said worm gear is a single lead thread.
 4. An anti-spin, anti-drift mechanism for a rotatable gear segment, said mechanism including: a worm gear meshing with said rotatable gear segment, an operating member rotatably mounted relative to said rotatable gear segment, and a bevel gear set operatively connecting said operating member and said worm gear.
 5. The anti-spin, anti-drift mechanism of claim 4 in which said bevel gear set includes a speed-up gear at one end of said worm gear and a drive gear connected to said operating member.
 6. The anti-spin, anti-drift mechanism of claim 5 in which said speed-up gear is a bevel gear.
 7. The anti-spin, anti-drift mechanism of claim 6 in which said bevel gear is formed integrally with said worm gear.
 8. The anti-spin, anti-drift assembly of claim 3 in which said worm gear is formed with a lead angle of said single lead thread having a tangent which is greater than the coefficient of friction of the engaging surfaces of said gear segment and said worm gear.
 9. The anti-spin, anti-drift assembly of claim 4 in which said worm gear is formed with a thread lead angle having a tangent which is greater than the coefficient of friction of the engaging surfaces of said gear segment and said worm gear. 